Che Adams has completed his £16m move from Birmingham to Southampton, becoming Ralph Hasenhuttl's second summer signing.
Forward Adams, who scored 22 goals last season, has signed a five-year deal after undergoing a medical on Sunday and agreeing personal terms.
The two clubs agreed a fee on Saturday ending Southampton's long-running pursuit of the 22 year-old.
They wanted to sign Adams in January but Birmingham refused to sell due to fears about being deep in trouble when their points deduction arrived and also without their biggest goal threat.
Southampton tested Birmingham's resolve again once the summer window opened and their third bid was finally enough to see them land their man.
Sportsmail revealed in May how Hasenhuttl planned to sign up to three new attackers and a commanding central defender.
As well as Adams he has also landed Malian winger Moussa Djenepo for £14m from Standard Liege and he will now step up his search for a centre-back.
Bristol City's Adam Webster, rated by some as the Championship's best centre-back, has been mooted.
But Bristol City have put a huge £30m price tag on Webster's head while his Portsmouth connections - he started his career at Southampton's biggest rivals - may also be an issue.
The sale of left-back Matt Targett to Aston Villa, in a deal worth up £17m which was also confirmed today, has covered the cost of Adams' purchase.
Southampton are also set to bring in further funds from the sale of striker Charlie Austin.
He and Hasenhuttl have agreed the time is right to move on for regular football and Aston Villa, Crystal Palace, West Brom and Fulham are all keen. Austin is likely to cost £10m.